Fe saponite, a layered silicate for reversible lithium-ions storage with large diffusion coefficient

A kind of layered Li 2 MSiO 4 material, Fe saponite with Na + pillaring (Na + -FSAP) was developed as a low-cost and environment-friendly lithium-ion storage material. The Na + -FSAP follows the insertion/deinsertion working mechanism accompanied by valence change of Fe from Fe 1.86+ to Fe 2.71+ (average value) after stabilization, and displays a specific capacity of 125 mAh g −1 at 50 mA g −1 with retention ratio of 80.8% after 75 cycles. The Na + -pillaring effect and abundant structural water in the gallery urge Li + migrate rapidly, resulting in a large Li + diffusion coefficient within a range of 10 −6.5 –10 −7.5  cm 2 s −1 . Thus, the Na + -FSAP provides a model material to design electrode materials with rapid lithium-ion migration and has great potential to take place of polyanionic-type Li 2 MSiO 4 (M = Mn, Fe, Co) cathode materials.